1. Field of the Invention
The present invention relates to an image forming apparatus characterized by conveyance control for an endless belt.
2. Description of the Related Art
In endless belt conveying apparatuses, there has been known a technique to enable a belt to travel with stability, while reducing an amount of shift of the traveling belt to a minimum. In the following, a description is given of an example where the belt is an intermediate transfer belt.
With this technique, a side edge position of the intermediate transfer belt is periodically detected by a sensor, and based on detection results, there are calculated an amount of change in intermediate transfer belt shift position, a shift speed, and a deviation of the shift position from a target position. Subsequently, a correction amount is derived and then supplied to a drive source that adjusts an inclination angle of a shift control roller on which the intermediate transfer belt is supported. Then, the roller inclination angle is adjusted by the drive source to realtime control the shift position of the intermediate transfer belt, whereby the side edge position of the intermediate transfer belt is stabilized near the target position (see, Japanese Laid-open Patent Publication No. 2005-326638).
It should be noted that the whole of an image forming apparatus is sometimes distorted due to, e.g., part tolerance, transportation of the apparatus, and/or distortion of an installation place for the apparatus. In that case, a rotating shaft of an intermediate transfer belt support roller is deviated from a desired direction and as a result, a shift speed of the intermediate transfer belt varies depending on directions, thus making it difficult for the above-described prior art to enable the intermediate transfer belt to travel at the target position with stability.
As a result, especially in a case that the intermediate transfer belt conveying apparatus is used in a color image forming apparatus, there is a fear that toner images of respective colors are deviated in their superposed position, resulting in out-of-color registration of a formed image.